drm/rockchip: dw_dp: Fix null-ptr-deref in dw_dp_remove()

In the Linux kernel, the following vulnerability has been resolved: drm/rockchip: dw_dp: Fix null-ptr-deref in dw_dp_remove() Attempting to access driver data in the platform driver ->remove() callback may lead to a null pointer dereference since there is no guaranty that the component ->bind() callback invoking platform_set_drvdata() was executed. A common scenario is when Rockchip DRM driver didn't manage to run component_bind_all() because of an (unrelated) error causing early return from rockchip_drm_bind(). Drop the unnecessary call to platform_get_drvdata() and, instead, reference the target device structure via platform_device.